Department of Medicine, Vanderbilt University Medical Center and Vanderbilt University School of Medicine, Nashville, Tennessee, USA.
Medical and Research Services, Department of Veterans Affairs Hospital, Tennessee Valley Healthcare System, Nashville, Tennessee, USA.
Acta Physiol (Oxf). 2022 Aug;235(4):e13826. doi: 10.1111/apha.13826. Epub 2022 May 18.
Erythropoietin (EPO) is regulated by hypoxia-inducible factor (HIF)-2. In the kidney, it is produced by cortico-medullary perivascular interstitial cells, which transdifferentiate into collagen-producing myofibroblasts in response to injury. Inhibitors of prolyl hydroxylase domain (PHD) dioxygenases (HIF-PHIs) activate HIF-2 and stimulate kidney and liver EPO synthesis in patients with anemia of chronic kidney disease (CKD). We examined whether HIF-PHIs can reactivate EPO synthesis in interstitial cells that have undergone myofibroblast transdifferentiation in established kidney fibrosis.
We investigated Epo transcription in myofibroblasts and characterized the histological distribution of kidney Epo transcripts by RNA in situ hybridization combined with immunofluorescence in mice with adenine nephropathy (AN) treated with HIF-PHI molidustat. Lectin absorption chromatography was used to assess liver-derived EPO. In addition, we examined kidney Epo transcription in Phd2 knockout mice with obstructive nephropathy.
In AN, molidustat-induced Epo transcripts were not found in areas of fibrosis and did not colocalize with interstitial cells that expressed α-smooth muscle actin, a marker of myofibroblast transdifferentiation. Epo transcription was associated with megalin-expressing, kidney injury molecule 1-negative nephron segments and contingent on residual renal function. Liver-derived EPO did not contribute to serum EPO in molidustat-treated mice. Epo transcription was not associated with myofibroblasts in Phd2 knockout mice with obstructive nephropathy.
Our studies suggest that HIF-PHIs do not reactivate Epo transcription in interstitial myofibroblasts and that their efficacy in inducing kidney EPO in CKD is dependent on the degree of myofibroblast formation, the preservation of renal parenchyma and the level of residual renal function.
促红细胞生成素（EPO）受缺氧诱导因子（HIF）-2 调控。在肾脏中，它由皮质-髓质血管周围间质细胞产生，这些细胞在受到损伤时会向产生胶原的肌成纤维细胞转分化。脯氨酰羟化酶结构域（PHD）双加氧酶（HIF-PHIs）抑制剂可激活 HIF-2，刺激慢性肾脏病（CKD）贫血患者的肾脏和肝脏 EPO 合成。我们研究了 HIF-PHIs 是否可以在已经发生纤维化的肾脏中经历肌成纤维细胞转分化的间质细胞中重新激活 EPO 合成。
我们研究了肌成纤维细胞中的 Epo 转录，并通过腺嘌呤肾病（AN）小鼠中 RNA 原位杂交与免疫荧光相结合的方法，结合用 HIF-PHI 莫立司他治疗的小鼠，研究了肾脏 Epo 转录本的组织学分布。用凝集素吸收色谱法评估肝脏来源的 EPO。此外，我们还研究了梗阻性肾病中 Phd2 敲除小鼠的肾脏 Epo 转录。
在 AN 中，莫立司他诱导的 Epo 转录本未在纤维化区域中发现，也未与表达α-平滑肌肌动蛋白（肌成纤维细胞转分化的标志物）的间质细胞共定位。Epo 转录与表达 megalin、肾脏损伤分子 1 阴性的肾单位段相关，且取决于残余肾功能。肝脏来源的 EPO 对莫立司他处理的小鼠血清中的 EPO 没有贡献。在梗阻性肾病的 Phd2 敲除小鼠中，Epo 转录与肌成纤维细胞无关。
我们的研究表明，HIF-PHIs 不会在间质肌成纤维细胞中重新激活 Epo 转录，它们在 CKD 中诱导肾脏 EPO 的疗效取决于肌成纤维细胞形成的程度、肾实质的保留和残余肾功能的水平。
